The present invention relates to hypodermic syringe needle assemblies, and more particularly concerns a needle assembly that has an improved protective sleeve to guard against inadvertent contact with the end of the cannula.
The standard hypodermic syringe includes a barrel and plunger and a needle assembly having a hub that is readily attachable to and detachable from an end of the barrel. The needle hub mounts the cannula, and in the standard needle assembly, a cannula guard cap is provided that is a hand tight friction fit on the hub. The cannula cap is removed for use of the syringe, and after use the cap may be replaced, or the needle may be inserted into a cork to seal the contents of the syringe. The required handling of the needle assembly after use, whether by replacing the cannula cap or inserting the cannula into a cork, exposes the health care worker to the possibility of accidental needle sticks. With the highly publicized spreading of blood-borne diseases, dangers of such accidental needle sticks are becoming of greater concern. The modern health care worker faces increased risk of contracting life threatening disease through on-the-job exposure at least partly due to accidental needle sticks.
The increased danger has stimulated increased effort toward providing needle assembly protection. Different types of protective devices have been suggested. Many of such devices, however, require some type of structure that is connected to or mounted upon the barrel of the syringe itself and remain connected to the barrel during use and handling of the syringe. This causes significant interference with the handling and use of the syringe, since the standard, relatively smooth and relatively small diameter barrel has now become encumbered with a protective device, which may prevent direct contact of the operator's fingers with the barrel itself. Other arrangements for needle protection, recognizing the problem that stems from the location of protection mounting structure on the syringe barrel, have provided special needle and guard assemblies requiring specially manufactured needles which are considerably longer and more costly than the standard needle assembly.
A widely used standard needle assembly includes a needle hub having an upper end that is formed with an arrangement for connecting the hub to an end of the syringe barrel, and having a lower end to which is fixedly secured the cannula. A standard syringe barrel has an end formed with what is commonly known as a leur tip. The leur tip is available in two forms. A leur slip tip is an elongated, slightly tapered connecting fitting or neck extending from the end of the barrel and formed integrally therewith. The slip tip taper is a hand tight friction fit with the interior of the upper section of the needle assembly hub, which thus can be firmly connected to or removed from the syringe barrel. In a second form of leur tip, the tapered connecting fitting or neck remains the same, but is surrounded by an internally threaded sleeve radially spaced from the slip tip neck. The standard needle assembly hub includes an upper flange having a pair of diametrically opposed, radially outwardly extending ears, which effectively form a pair of thread elements that threadedly engage the internal threads on the leur tip threaded sleeve. In this arrangement the needle assembly hub can be threadedly engaged with the leur tip, and, at the same time, connected to the tip neck with a tight frictional fit for more firm securement. The widely used standard needle assembly thus is particularly configured for use with the widely used leur tip syringe of either configuration. Therefore, it is important that a needle guard be usable with the standard needle assembly and the standard leur tip syringe.
Accordingly, it is an object of the present invention to provide a needle guard that may be used with standard needle assemblies and syringes and avoids problems of prior devices.